Emulating A Remote Control Ceiling Fan Transmitter In An FPGA

[Joel] has a remote control ceiling fan. It’s nothing special, the controller has a low-power 350MHz transmitter and a Holtek encoder to send commands by keying the transmitter’s output. Desiring something a little better, he set about reverse engineering the device’s protocol and implementing it on a Lattice iCE40 FPGA.

To decode the device’s packets he reached for his RTL-SDR receiver and took a look at it in software. GQRX confirmed the presence of the carrier and allowed him to record a raw I/Q file, which he could then supply to Inspectrum to analyse the packet structure. He found it to be a simple on-off keying scheme, with bits expressed through differing pulse widths. He was then able to create a Gnu Radio project to read and decode them in real time.

Emulating the transmitter was then a fairly straightforward process of generating a 350MHz clock using the on-board PLL and gating it with his generated data stream to provide modulation. The result was able to control his fan with a short wire antenna, indeed he was worried that it might also be doing so for other similar fans in his apartment complex. You can take a look at his source code on GitHub if you would like to try something similar.

It’s worth pointing out that a transmitter like this will radiate a significant amount of harmonics at multiples of its base frequency, and thus without a filter on its output is likely to cause interference. It will also be breaking all the rules set out by whoever the spectrum regulator is where you live, despite its low power. However it’s an interesting project to read, with its reverse engineering and slightly novel use of an FPGA.

Wireless remote hacking seems to be a favorite pastime here in the Hackaday community. We’ve had 2.4GHz hacks and plenty of wireless mains outlet hacks.

Mag Lev Without The Train (But With An FPGA)

It always surprises us that magnetic levitation seems to have two main purposes: trains and toys. It is reasonably inexpensive to get floating Bluetooth speakers, globes, or just floating platforms for display. The idea is reasonably simple, especially if you only care about levitation in two dimensions. You let an electromagnet pull the levitating object (which is, of course, ferrous). A sensor detects when the object is at a certain height and shuts off the magnet. The object falls, which turns the magnet back on, repeating the process. If you do it right, the object will reach equilibrium and hover near the sensor.

Some students at Cornell University decided to implement the control loop to produce levitation using an Altera FPGA. An inductive sensor determined the position of an iron ball. The device uses a standard proportional integral derivative (PID) control loop. The control loop and PWM generation occur in the FPGA hardware. You can see a video of their result, below.

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No Frame Buffer for FPGA VGA Graphics

Usually, when you think of driving a VGA–in software or hardware–you think of using a frame buffer. The frame buffer is usually dual port RAM. One hardware or software process fills in the RAM and another process pulls the data out at the right rate and sends it to the VGA display (usually through a digital to analog converter).

[Connor Archard] and [Noah Levy] wanted to do some music processing with a DE2-115 FPGA board. To drive the VGA display, they took a novel approach. Instead of a frame buffer, they use the FPGA to compute each pixel’s data in real-time.

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FPGA Powers Blazingly Fast LED Matrix Audio Visualizer

[Sam Miller], [Sahil Gupta], and [Mashrur Mohiuddin] worked together on a very fast LED matrix display for their final project in ECE 5760 at Cornell University.

Real time!
Real time!

They started, as any good engineering students, by finding a way to make their lives easier. [Sam] had built a 32×32 LED matrix for another class. So, they made three more and ended up with a larger and more impressive 64×64 LED display.

They claim their motivation was the love of music, but we have a suspicion that the true reason was the love all EEs share for unnaturally bright LEDs; just look at any appliance at night and try not be blinded.

The brains of the display is an Altera DE2-115 FPGA board. The code is all pure Verilog. The FFT and LED control are implemented in hardware on the FPGA; none of that Altera core stuff. To generate images and patterns they wrote a series of python scripts. But for us it’s the particle test shown in the video below that really turns our head. This system is capable of tracking and reacting to a lot of different elements on the fly why scanning the display at about 310 FPS. They have tested display scanning at twice that speed but some screen-wrap artifacts need to be worked out before that’s ready for prime time.

The team has promised to upload all the code to GitHub, but it will likely be a while before the success hangover blows over and they can approach the project again. You can view a video interview and samples of the visualizations in the videos after the break.

Thanks to their Professor, [Bruce Land], for submitting the tip! His students are always doing cool things. You can even watch some of his excellent courses online if you like: Here’s one on the AVR micro-controller.

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FPGA-and-Pi Colossus Smashes Your Codes!

If it were sixty years ago, and you were trying to keep a secret, you’d be justifiably glad that [Ben North] hadn’t traveled back in time with his Raspberry-Pi-and-FPGA code-breaking machine.

We’ve seen a lot of Enigma builds here at Hackaday — the World War II era encryption machine captured our readers’ imaginations. But perhaps the more important machines to come out of cryptanalysis during that era were Turing’s electromechanical Bombe, because it cracked Enigma, and the vacuum-tube-based Colossus, because it is one of the first programmable electronic digital computers.

[Ben]’s build combines his explorations into old-school cryptanalysis with a practical learning project for FPGAs. If you’re interested in either of the above, give it a look. You can start out with his Python implementations of Colossus to get your foot in the door, and then move on to his GitHub repository for the FPGA nitty-gritty.

It’s also a cool example of a use for the XuLA2 FPGA board and its companion StickIt board that plug straight into a Raspberry Pi for programming and support. We haven’t seen many projects using these since we first heard about them in 2012. This VirtualBoy hack jumped out at us, however. It looks like a nice platform. Anyone else out there using one?

Real-Time FPGA Finger Detection

The student projects that come out of [Bruce Land]’s microcontroller- and FPGA-programming classes feature here a lot, simple because some of them are amazing, but also because each project is a building-block for another. And we hope they will be for you.

This time around, [Junyin Chen] and [Ziqi Yang] created a five-in-a-row video game that is controlled by a pointing finger. A camera, pointed at the screen, films the player’s hand and passes the VGA data to an FPGA. And that’s where things get interesting.

An algorithm in the FPGA detects skin color and, after a few opening and closing operations, comes up with a pretty good outline of the hand. The fingertip localization is pretty clever. They sum up the number of detected pixels in the X- and Y-axis, and since a point finger is long and thin, locate the tip because it’s going to have a maximum value in one axis and a minimum along the other. Sweet (although the player has to wear long sleeves to make it work perfectly).

How does the camera not pick up the game going on in the background? They use a black-and-white game field that the skin-color detection simply ignores. And the game itself runs in a Nios embedded processor in the FPGA. There’s a lot more detail on the project page, and of course there’s a demo video below.

We love to follow along with Prof. Land‘s classes. His video series is invaluable, and the course projects have been an inspiration.

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Hand Gestures Play Tetris

There are reports of a Tetris movie with a sizable budget, and with it come a plentiful amount of questions about how that would work. Who would the characters be? What kind of lines would there be to clear? Whatever the answers, we can all still play the classic game in the meantime. And, thanks to some of the engineering students at Cornell, we could play it without using a controller.

This hack comes from [Bruce Land]’s FPGA design course. The group’s game uses a video camera which outputs a standard NTSC signal and also does some filtering to detect the user. From there, the user can move their hands to different regions of the screen, which controls the movement of the Tetris pieces. This information is sent across GPIO to another FPGA which uses that to then play the game.

This game is done entirely in hardware, making it rather unique. All game dynamics including block generation, movement, and boundary conditions are set in hardware and all of the skin recognition is done in hardware as well. Be sure to check out the video of the students playing the game, and if you’re really into hand gesture-driven fun, you aren’t just limited to Tetris, you can also drive a car.

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